This invention relates to a liquid jetting apparatus having a head capable of jetting a drop of liquid from a nozzle. In particular, this invention is related to a liquid jetting apparatus that can prevent viscosity of liquid in a nozzle of a head from increasing.
In a ink-jetting recording apparatus such as an ink-jetting printer or an ink-jetting plotter (a kind of liquid jetting apparatus), a recording head (head) can be moved in a main scanning direction, and a recording paper (a kind of recording medium) can be moved in a sub-scanning direction perpendicular to the main scanning direction. While the recording head is moved in the main scanning direction, a drop of ink can be jetted from a nozzle of the recording head onto the recording paper. Thus, an image including a character or the like can be recorded on the recording paper. For example, the drop of ink can be jetted by changing pressure of the ink in a pressure chamber communicating with the nozzle.
The pressure of the ink may be changed by utilizing a pressure-generating member, for example a heating member or a piezoelectric vibrating member. In a former case, the heating member can generate a Joule heat based on a supplied driving-pulse in order to generate an air bubble in the pressure chamber. When a volume of the air bubble is changed, the pressure of the ink in the pressure chamber may be changed. Then, the drop of ink is jetted from the nozzle. In a latter case, the piezoelectric vibrating member can be deformed based on a supplied driving-pulse in order to change a volume of the pressure chamber. When the volume of the pressure chamber is changed, the pressure of the ink in the pressure chamber may be changed. Then, the drop of ink is jetted from the nozzle.
The ink in the nozzles of the recording head is held by surface tension thereof and exposed to air. Thus, solvent of the ink such as water may gradually evaporate to increase a viscosity of the ink in the nozzle. In the case, quality of recorded images may deteriorate because the ink having a great viscosity may be jetted toward a direction deviated from a normal direction. In addition, in the case, drops of the ink having uneven volumes may be jetted.
To prevent the viscosity of the ink in the nozzles from increasing, some measures have been proposed. One of the measures is to forcibly discharge (jet out) ink having an increased viscosity from the nozzle outside an objective recording area (flushing operation). Another one of the measures is to cause a meniscus of the ink to minutely vibrate to stir the ink (stirring operation). The meniscus means a free surface of the ink exposed at an opening of the nozzle.
Such a conventional measure is conducted in such a uniform operational condition that a normal ink-jetting operation can be achieved even if the viscosity of the ink in the nozzle tends to increase most. For example, if a recording apparatus can perform a recording operation by using any of a large drop of the ink, a middle drop of the ink and a small drop of the ink, the viscosity of the ink in the nozzle tends to affect the printing operation most when the small drop of the ink is used. Thus, the recovering measure (flushing operation or micro-vibrating operation) is conducted in such an operational condition that a normal recording operation can be achieved even when the small drop of the ink is used.
However, when the middle drop of the ink or the large drop of the ink is used for the recording operation, the ink is consumed so much that the normal recording operation can be achieved with less recovering operations. That is, the above uniform condition for the recovering measure may cause too many recovering operations, which means that the pressure-generating member may be driven in vain. That is, electric power may be consumed more and a lifetime of the pressure-generating member may be shortened. In addition, if a flushing operation is performed, the ink may be consumed in vain.
The object of this invention is to solve the above problems, that is, to provide a liquid jetting apparatus such as an ink-jet recording apparatus that can more efficiently conduct a maintenance (recovering) operation for preventing viscosity of ink in a nozzle from increasing in order to keep a condition for jetting a drop of the ink in good one.
In order to achieve the object, a liquid jetting apparatus includes: a head having a nozzle, a recovering unit that can recover a suitable viscosity of liquid in the nozzle from an increased viscosity thereof, a pressure-generating unit that can change a pressure of liquid in the nozzle in order to jet a drop of the liquid from the nozzle, based on jetting data, an obtaining unit that can obtain minimum-volume information of the drop of the liquid to be jetted from the nozzle by the pressure-generating unit, and a controller that can control the recovering unit, based on the minimum-volume information obtained by the obtaining unit.
According to the feature, since the recovering unit is controlled based on the minimum-volume information of the drop of the liquid to be jetted from the nozzle, a recovering operation for recovering the suitable viscosity of the liquid in the nozzle can be performed more efficiently, dependently on a state of the liquid in the nozzle.
If the head can move in a main scanning direction, preferably, the pressure-generating unit can jet a plurality of drops of the liquid having different volumes from the nozzle during one scanning movement, and the obtaining unit can obtain a least volume of the plurality of drops of the liquid to be jetted by the pressure-generating unit, as the minimum-volume information. In the case, a suitable recovering operation can be performed for each of the scanning movements.
Preferably, the obtaining unit is adapted to obtain the minimum-volume information of the drop of the liquid to be jetted from the nozzle, based on the jetting data. In the case, the minimum-volume information of the drop of the liquid can be obtained more easily.
Alternatively, the obtaining unit is adapted to obtain the minimum-volume information of the drop of the liquid, by measuring a least volume of the drop of the liquid actually jetted from the nozzle. In the case, the minimum-volume information of the drop of the liquid can be obtained more exactly.
Preferably, the controller is adapted to control the recovering unit, based on information about a kind of the liquid. In the case, an efficient recovering operation can be performed suitably for the kind of the liquid.
If the head is connected to a liquid cartridge that can supply the liquid to the head, the liquid cartridge is preferably provided with a kind-information storage that can store the information about the kind of the liquid in the liquid cartridge. In the case, the information about the kind of the liquid can be handled more easily.
In addition, preferably, the controller is adapted to control the recovering unit, based on an output from a sensor that can detect a state of environment where the liquid jetting apparatus is used. In the case, an efficient recovering operation can be performed suitably for the state of environment where the liquid jetting apparatus is used.
In addition, preferably, the controller is adapted to control the recovering unit, based on an output from a temperature sensor that can detect a temperature of the liquid in or near to the nozzle. In the case, an efficient recovering operation can be performed suitably for a state of the increased viscosity of the ink corresponding to a change of the temperature.
For example, the recovering unit is adapted to perform a micro-vibrating operation during which a meniscus of the liquid in the nozzle is caused to minutely vibrate. In the case, the controller may be adapted to change a number of micro-vibrations in the micro-vibrating operation performed by the recovering unit, based on the minimum-volume information obtained by the obtaining unit. Alternatively, the controller may be adapted to change a repeating cycle of the micro-vibrating operation performed by the recovering unit, based on the minimum-volume information obtained by the obtaining unit. Alternatively the controller may be adapted to change an amplitude the micro-vibrating operation performed by the recovering unit, based on the minimum-volume information obtained by the obtaining unit.
Alternatively the recovering unit is adapted to perform a flushing operation during which drops of the liquid in the nozzle having an increased viscosity are discharged. In the case, the controller may be adapted to change a number of the drops of the liquid discharged in the flushing operation performed by the recovering unit, based on the minimum-volume information obtained by the obtaining unit. Alternatively, the controller may be adapted to change a discharging period of the drops of the liquid discharged in the flushing operation performed by the recovering unit, based on the minimum-volume information obtained by the obtaining unit. Alternatively, the controller may be adapted to change a performing period of a plurality of flushing operations performed by the recovering unit, based on the minimum-volume information obtained by the obtaining unit.
In addition, a controlling unit for controlling a liquid jetting apparatus including: a head having a nozzle; a recovering unit that can recover a suitable viscosity of liquid in the nozzle from an increased viscosity thereof; a pressure-generating unit that can change a pressure of liquid in the nozzle in order to jet a drop of the liquid from the nozzle, based on jetting data; and an obtaining unit that can obtain minimum-volume information of the drop of the liquid to be jetted from the nozzle by the pressure-generating unit; is characterized by that the controlling unit comprises a controller that can control the recovering unit, based on the minimum-volume information obtained by the obtaining unit.
A computer system can materialize the whole controlling unit or only one or more components in the controlling unit.
This invention includes a storage unit capable of being read by a computer, storing a program for materializing the controlling unit in a computer system.
This invention also includes the program itself for materializing the controlling unit in the computer system.
This invention includes a storage unit capable of being read by a computer, storing a program including a command for controlling a second program executed by a computer system including a computer, the program is executed by the computer system to control the second program to materialize the controlling unit.
This invention also includes the program itself including the command for controlling the second program executed by the computer system including the computer, the program is executed by the computer system to control the second program to materialize the controlling unit.
The storage unit may be not only a substantial object such as a floppy disk or the like, but also a network for transmitting various signals.